1. Field of the Invention
The present invention relates in general to the field of laminating films. More particularly, the present invention relates to a film having antibiotic and/or biostatic properties. Specifically, a preferred embodiment of the present invention relates to a laminating film having a first layer, a second layer, and a third layer incorporating properties to neutralize and/or destroy a variety of harmful organisms including bacteria, fungus, yeast, and viruses.
2. Discussion of the Related Art
As is known to those skilled in the art, germs and other infectious agents are everywhere. In public places, such as restaurants, the number of bacteria is often very large on items used and handled by employees and customers alike. For example, menus, placemats, recipe sheets, countertops, etc. contain thousands of potentially harmful microbes. The same is true for frequently used and handled items in other public places such as hospitals and grocery stores.
Various antibiotic compounds exist which may be used to combat some of these harmful microbes. For example, “ceramics” are commonly used to prevent bacterial growth. The “ceramics” employed in the present invention include zeolites, hydroxyapatite, zirconium phosphates or other ion-exchange ceramics. The use of Hydroxyapatite particles is described, e.g., in U.S. Pat. No. 5,009,898. Zirconium phosphates containing antibiotic metals are described, e.g., in U.S. Pat. Nos. 5,296,238; 5,441,717; and 5,405,644. Copper or Zinc zeolites are used, while silver zeolites are also popular for such application, as described in U.S. Pat. No. 6,248,342. Zeolites are preferred, and are described more fully in the preferred embodiments referred to below.
Zeolites are three-dimensional, microporous, crystalline solids with well-defined structures that contain aluminum, silicon, and oxygen in their regular framework; cations and water are located in void spaces in the pores. The silicon and aluminum atoms are tetrahedrally coordinated with each other through shared oxygen atoms. While zeolites are natural minerals, most zeolites used commercially are produced synthetically. Such antibiotic zeolite particles are well-known and can be prepared for use in the present invention using known methods. These include the antibiotic zeolites disclosed, for example, in U.S. Pat. Nos. 4,938,958 and 4,911,898. Because of their regular and reproducible structure, zeolites behave in a predictable fashion.
In the presence of moisture, the zeolite acts as an ion pump providing the controlled time release of silver ions into the environment in exchange for sodium ions from the environment. This controlled release provides continuous antibiotic protection for the product. As humidity increases and the environment becomes ideal for bacteria growth, more ions are released.
Laminated materials are commonly found throughout numerous industries. A layer of laminate provides readily used and handled materials, such as paper goods used in for example, menus or medical documents, with an outer defense layer. The laminate layer provides a coating that allows the underlying paper to be reused and recirculated while resisting the detrimental physical effects of repeated use. Use of a laminate results in a material that is resistant to tears, spills and other common detrimental effects such as scratching, fading and smudging. The most desirable laminates have sufficient clarity to provide ease of viewing the underlying printed material and are resistant to scuffing.
Thermal lamination is considered by many in the graphic arts community to be the finish of choice. With its attractive look and luxurious feel, a thermal laminated product communicates quality and creates a favorable impression with the consuming public. Thermal laminating materials (hereinafter thermolaminates) and methods are known for protecting printed substrates by adhering a protective thermoplastic polymer cover film or sheet to one or both of the major surfaces of a printed substrate. There are a wide variety of laminates to choose from, i.e., clear, delustered, satin finish, and glueable-stampable, to name but a few. See U.S. Pat. No. 6,153,298.
While known laminates provide a barrier against physical deterioration, they do little if anything to prevent the spread of harmful microbes on the surface of the laminate. Due to the widespread use of laminated materials in environments prone to bacteria, such as grocery stores and restaurants, it is desirable to have a laminating film that has antibiotic properties to resist the spread of bacterial and other unwanted microbial contaminants in addition to providing the known physical advantages.
Despite the desirability of providing such an antibiotic laminating film, previous attempts at providing such a film have proven unsatisfactory for the majority of the graphic arts industry. To date, an obvious need exists for a laminating film that provides a durable, transparent outer covering and additionally prevents the growth of microbial contaminants on the surface of the laminated material. An antibiotic and/or biostatic thermal lamination would add value to a wide range of printed materials such as library book covers, magazines, specialty packaging, posters, photographs, maps, and menus to name but a few.